Fuel injection pump for internal combustion engines

Abstract

The invention is based on a fuel injection pump in which to supply a very rapid pressure rise in the interior of a fuel injection pump, a pressure valve controlling this pressure is modified such that upon cold starting of the engine, the pressure valve closes a bypass line at the feed pump and thus delivers all the fuel to the fuel injection pump. The closure is effected as a function of rpm and accordingly pressure, and also as a function of the engine operating temperature; in the fuel injection pump according to the invention, the rpm- and pressure-dependent diversion is performed by the adjusting piston of an injection adjuster. Thus, compared with the known cold-starting accelerating devices, one additional pressure limiting valve can be eliminated.

What is claimed and desired to be secured by letters patent of the United States is: 
     
       1. A fuel injection pump for internal combustion engines, having an injection adjuster (2) that has an adjusting piston (4) that is displaceable in a cylinder (3), said adjusting piston on one face end encloses a work chamber (6), exposed to a control pressure controlled as a function of rpm, in the cylinder (3) and on the other face end defines a restoring chamber (9), which contains a spring (5) acting upon the adjusting piston (4) with a restoring force, and which chamber is relieved via a return line (13); to a fuel tank a feed pump (15) driven in synchronism with the fuel injection pump, the feed pressure of said feed pump is controlled as a control pressure by a pressure control valve (19), which has a wall, acted upon by the control pressure, said wall is adjustable counter to a restoring spring (26), the adjustable wall divides a pressure chamber (22) from a restoring chamber (25) that receives the restoring spring (26) and communicates continuously with the pressure chamber (22) via a throttle bore (27), whereupon with the control motion of the adjustable wall in the pressure control valve (19), an outflow line (23) from the pressure chamber (22) to a relief chamber is controlled and the restoring chamber (25) is relieved via a pressure holding valve (30) with temperature-dependent actuation and via a pressure limiting valve, said pressure limiting valve has a control piston acted upon by the control pressure and is adjustable counter to a restoring spring, by means of said control piston, the flow cross section of a relief line communicating with the restoring chamber is controllable, acting as the control piston of the pressure limiting valve for the relief of the pressure control valve restoring chamber (25) of the feed pump (15) is an adjusting piston (4) of the injection adjuster (2), said adjusting piston has a control opening on a jacket face, the opening being defined by a control edge and communicating with the restoring chamber (9), said control opening communicates with the relief line (29) of the restoring chamber (25) beyond a predetermined displacement position of the adjusting piston which discharges into the cylinder (3).